The invention relates to a cross-coil rotary magnet device having a rotor which is mounted for rotation together with a shaft, the rotor consisting, in particular, of a permanent magnet with diametrically opposite permanent magnet poles, and having a coil arrangement with coils which are arranged at an angle of, in particular, 90.degree. from each other.
Such a known cross-coil rotary magnet device is developed especially as a motor for driving a clockwork (Federal Republic of Germany OS No. 34 19 100). In that motor a rotatably mounted rotor has diametrically opposite permanent magnet poles. A multi-phase coil arrangement serves to produce a magnetic field which deflects the rotor as a function of control signals which are applied to coils of the coil arrangement. The coil arrangement has, for this purpose, a plurality of coils which are arranged at an equal angular distance apart, the coils surrounding the rotor and being controlled by sinusoidal voltages which are shifted apart in phase. The coil arrangement consists, in particular, of two coils which are arranged at right angles to each other and are fed with two sinusoidal voltages spaced 90.degree. apart.
The axis of rotation or shaft can serve as the seconds shaft or minutes shaft of a clockwork. In the latter case, a minute hand is fastened on one end of the rotary shaft, which minute hand can be moved over a dial. An hour wheel is driven by a drive pinion disposed on the rotary shaft and a minute wheel, the hour wheel having an hour collar or tube surrounding the rotary shaft. An hour hand which can be moved over the dial is fastened on the hour tube.
In this motor, as in the case of other known cross-coil rotary magnet devices, a special development for a specific purpose of use, in this case for the driving of a clockwork, and which permits other use of the cross-coil rotary magnet arrangement only with extensive limitations or structural changes, is disadvantageous. Since the motor must be continuously fed with sinusoidal voltages, a correspondingly high expenditure of energy must be expected.
This motor, which is developed for driving a clockwork and has a drive pinion, minute wheel and hour wheel as well as an hour tube is, for instance, not suitable generally as device for indicating a mechanical measurement variable, in particular the speed of a motor vehicle.
In the known device for indicating a mechanical variable, in particular the speed of a motor vehicle, a measuring mechanism is provided which serves to displace a pointer and which, via a converter, is connected to a transmitter which produces a pulse at a pulse frequency which is proportional to a measurement variable (Federal Republic of Germany No. OS 27 30 699). A stepping motor which travels forward and backward serves as measuring mechanism. The stepping motor is fed with a direction-evaluated train of pulses which result from counting values formed during successive defined time intervals as a function of the measurement variable and which, when compared with each other, give a sign-evaluated difference. The stepping motor, which adjusts itself in accordance with said difference, is coupled to a dial mechanism via a gearing. Such a stepping motor, if constructed, would not be readily suitable for other applications, for instance as setting member, ratio meter or sensor.